Probability of occurrence and study of earthquake recurrence models for gujarat state in India.

Abstract

The probabilistic approach and number of statistical distributions have been adopted by various researchers for computation of seismic risk in terms of conditional probabilities of future earthquakes and earthquake recurrence rates. Using the earthquake catalogue prepared by Institute of Seismological research - Gandhinagar, Gutenberg-Richter (G-R) parameters are then estimated to quantify seismic risk for three seismictectonically different regions i.e. Saurashtra, Kachchh and Mainland Gujarat. Based on the G-R parameter estimated, seismic risk in terms of probability of earthquake occurrence and earthquake return periods are estimated for the three regions of Gujarat. Further, to study earthquake recurrence in Gujarat state, four typical probability density models viz. Exponential, Rayleigh, Pareto and Weibull, have been studied to describe earthquake recurrence time to estimate the next large earthquakes in Gujarat state of India. Time intervals for the occurrence of the next large earthquake in the three region of Gujarat state have been estimated by maximization of conditional probability of earthquake occurrence. Specified four typical probability density models have been checked for its validity for Gujarat based on the last five earthquake event reported. The time interval between the earthquake events have been predicted and compared with observed time for its validation. It is observed that Kachchh region is governing the seismicity in Gujarat state and has high seismic risk compared to other two regions. Comparing the estimated earthquake recurrence interval with the observed data for the last five earthquakes, it is observed that Exponential and Weibull models are appropriate for Gujarat region. Rayleigh Model observed to be giving overestimated recurrence time whereas Pareto Model gives very small recurrence time interval for the Gujarat region.